Method for forming a three-dimensional object

ABSTRACT

A method for forming a three-dimensional object by extruding ink droplets from ink-jet heads includes forming an inner build region of the object. A colored region is formed outside of the inner build region so as to color the object. A support region is formed outside of the colored region so as to support the object while the object is being formed. An intermediate region is formed between the inner build region and the colored region. The intermediate region is formed in such a manner that affinity between the intermediate region and the inner build region and affinity between the intermediate region and the colored region are higher than affinity between the colored region and the support region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2016-159025, filed Aug. 12, 2016. Thecontents of this application are incorporated herein by reference intheir entirety.

BACKGROUND Field of the Invention

The present invention relates to a method for forming athree-dimensional object, a three-dimensional-object forming apparatus,and a non-transitory computer readable medium storing a program for thethree-dimensional-object forming apparatus.

Discussion of the Background

As a method for forming a three-dimensional object, in addition to sheetlamination as disclosed in Japanese Unexamined Patent ApplicationPublication No. 2003-71530, fused deposition molding (FDM), ink-jettechnology, ink-jet binder technology, stereo lithography (SL), andselective laser sintering (SLS), for example, have been known.

Among these methods, as an ink-jet technology, a method of injectingultraviolet curable resins and depositing layers of patterns by a 3Dprinter has been adopted with high frequency. In this method, afterdesigns, mechanisms, and other information of external and internalappearances of an end product are converted into data by athree-dimensional CAD, the data is sliced into multi-layered patterndata in a manner like deposition of thin sheets by a computer. Then, theultraviolet curable resins are injected from heads based on the patterndata to form build material layers, and the build material layers aredeposited to produce a three-dimensional object.

Moreover, decoration (patterns and other design features, and colors) ofthe three-dimensional object formed by such a method has been known.

The contents of Japanese Unexamined Patent Application Publication No.2003-71530 are incorporated herein by reference in their entirety.

In a case in which formation of a three-dimensional object in an ink-jettechnology is performed by additive manufacturing of depositing aplurality of ink layers, the plurality of ink layers, which correspondto a plurality of sections into which the three-dimensional object isdivided in a build direction, are to be formed in sequence. In thiscase, each of the ink layers includes a center region corresponding toan external shape of the three-dimensional object, a colored regionsurrounding an outer circumference of the center region, and a supportregion (support region) surrounding the colored region. The centerregion, the colored region, and the support region are respectivelyformed by extruding an ink for the center region, an ink for decoration(such as coloring inks of yellow, magenta, cyan, black, and othercolors), and an ink for the support region from heads corresponding tothe respective inks.

In this method, the support region is provided to support other inklayers deposited on an upper side of the three-dimensional object, andthe support region is to be removed after forming the three-dimensionalobject.

After formation of the three-dimensional object in the ink-jettechnology is performed by additive manufacturing, and when the supportregion is removed, however, a color quality of the obtainedthree-dimensional object (object) may be unfortunately degraded. Inlight of the above circumstances, there has been a demand for improvingthe color quality of the three-dimensional object finally obtained.

SUMMARY

According to one aspect of the present invention, a method for forming athree-dimensional object by extruding ink droplets from ink-jet headsincludes: forming an inner build region of the object; forming a coloredregion outside of the inner build region so as to color the object;forming a support region outside of the colored region so as to supportthe object while forming the object; and forming an intermediate regionbetween the inner build region and the colored region. The intermediateregion is formed in such a manner that affinity between the intermediateregion and the inner build region and affinity between the intermediateregion and the colored region are higher than affinity between thecolored region and the support region.

The inventor of the present disclosure has found that when surfaceroughness of the colored region after removing the support regionincreases, a color quality of the formed three-dimensional object isunfortunately degraded. The inventor conducted research and study onwhat causes an increase in the surface roughness of the colored region.As a result, the inventor has realized that in forming each ink layer,as a degree of mixing of an ink composite of the colored region and anink composite of the support region at an interface between the coloredregion and the support region increases, the surface roughness of thecolored region after removing the support region increases. In light ofthe above circumstances, the inventor has concluded to interpose theintermediate region between the inner build region and the coloredregion so as to make affinity between the colored region and the innerbuild region higher than affinity between the colored region and thesupport region. This suppresses mixing of the inks at the interfacebetween the colored region and the support region so as to improve thesurface roughness of the colored region after removing the supportregion. Thus, the three-dimensional object finally obtained has animproved color quality.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present disclosure and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of an exemplary three-dimensional objectformed by a forming apparatus according to an embodiment;

FIG. 2 is a cross-sectional view of the three-dimensional object formedby the forming apparatus;

FIGS. 3A and 3B illustrate a configuration of the forming apparatus;

FIG. 4 illustrates three-dimensional data of the three-dimensionalobject formed by the forming apparatus;

FIG. 5 is a diagram illustrating an ink layer formed based on slice dataof the three-dimensional object formed by the forming apparatus;

FIG. 6 is a flowchart of formation of the three-dimensional object bythe forming apparatus;

FIGS. 7A and 7B illustrate a distribution of ink composites in an inklayer at some midpoint in forming the three-dimensional object, and asurface state of the ink layer; and

FIGS. 8A and 8B illustrate a distribution of ink composites in an inklayer at some midpoint in forming a three-dimensional object accordingto a comparative example and a surface state of the ink layer.

DESCRIPTION OF THE EMBODIMENT

An embodiment of the present invention will now be described withreference to the accompanying drawings, wherein like reference numeralsdesignate corresponding or identical elements throughout the variousdrawings.

FIG. 1 is a perspective view of an exemplary three-dimensional object Tformed by a forming apparatus 10;

FIG. 2 is a cross-sectional view of the three-dimensional object T takenalong a plane A in FIG. 1. With virtual lines, FIG. 2 illustrates asupport region 53 formed along with the three-dimensional object T whenthe forming apparatus 10 forms the three-dimensional object T;

FIG. 3A schematically illustrates the configuration of the formingapparatus 10; and

FIG. 3B is a plan view of a head 20 of the forming apparatus 10, asviewed from below on a platform 11 side.

Three-Dimensional Object T

First, the three-dimensional object T formed by the forming apparatus 10will be described. As illustrated in FIGS. 1 and 2, thethree-dimensional object T according to the embodiment is formed bycovering a surface of an inner build region 50 with an intermediateregion 51 and a colored region 52 in this order. The inner build region50 is formed of an ink composite of white (W). The intermediate region51 includes the ink composite of white (W) and a transparent (CL) inkcomposite. The colored region 52 includes an ink composite containingcoloring components (Color), and the transparent (CL) ink composite.

The three-dimensional object T has an upper end T1 and a lower end T2,which are flat surfaces parallel to each other. The three-dimensionalobject T has such a circular shape that an outer diameter of thethree-dimensional object T increases as distances from the upper end T1and the lower end T2 increase, and that an approximately central portionof the three-dimensional object T in a height direction has the largestouter diameter. When the three-dimensional object T is formed by theforming apparatus 10, as illustrated in FIG. 2, an approximately halfportion of the three-dimensional object T on a lower side is coveredwith the support region 53 so as to form a three-dimensional object T′.After that, the support region 53 is removed to obtain thethree-dimensional object T.

The inner build region 50 is a center region of the three-dimensionalobject T. The light-reflecting white (W) ink composite is cured to makethe inner build region 50 have an external shape in accordance with ashape of the three-dimensional object T. In the embodiment, the innerbuild region 50 is solid in such a manner that an inside of the innerbuild region 50 is densely filled with the white (W) ink composite. Theinner build region 50, however, may be hollow.

The inner build region 50 is provided to reflect light that has enteredfrom a surface of the three-dimensional object T. This improves visualrecognizability of the colored region 52 outside of the inner buildregion 50. In light of the above circumstances, it suffices that atleast a range of the inner build region 50 having a predeterminedthickness on the surface side alone is formed of the light-reflectingwhite (W) ink composite.

The intermediate region 51 includes the white (W) ink composite and thetransparent (CL) ink composite, and is formed by curing these inkcomposites. The intermediate region 51 covers the whole surface of theinner build region 50 and has a predetermined thickness. Theintermediate region 51 is provided to enhance affinity between thecolored region 52, which covers a surface of the intermediate region 51,and the inner build region 50.

The colored region 52 is a mixed region formed of the ink composite,which includes, for example, Y (yellow), M (magenta), C (cyan), and K(black) as the coloring components, and the transparent (CL) inkcomposite. The colored region 52 is formed by curing these inkcomposites. The colored region 52 covers the whole surface of theintermediate region 51. The ink composite, which includes Y (yellow), M(magenta), C (cyan), K (black), and other colors as the coloringcomponents, lands on the colored region 52 at a predetermined ratio inaccordance with a target color. The color that the colored region 52assumes appears on the surface of the three-dimensional object T.

It should be noted that an ink composite in the colored region 52 shouldnot be necessarily limited to the ink composite including theabove-described coloring components such as Y (yellow), M (magenta), C(cyan), and K (black). Other than the transparent (CL) ink composite,the colored region 52 may include the white (W) ink composite.Alternatively, the colored region 52 may include an ink composite toshow a neutral color obtained by mixing Y (yellow), M (magenta), and C(cyan) in a combination as desired.

The support region 53 is formed by curing an ink composite (supportmaterial composite). In forming the three-dimensional object T bydepositing ink layers L, described later, in the height direction, thesupport region 53 is provided to support a lower surface of the regionwhere no other ink layers exist below some of the ink layers on aplatform 11 side so as to support the ink layers concerned (see FIG. 4).

Forming Apparatus 10

As illustrated in FIG. 3A, the forming apparatus 10 includes theplatform 11 of the three-dimensional object T, a head 20, and acontroller 30. The head 20 is arranged to be movable in a main scanningdirection Y on an upper side of the platform 11. The controller 30controls the forming apparatus 10. The forming apparatus 10 furtherincludes a main scanning driver 40 and a sub-scanning driver 45. Themain scanning driver 40 causes the head 20 to move in the main scanningdirection Y in accordance with an instruction from the controller 30.The sub-scanning driver 45 causes the head 20 to move in thesub-scanning direction X in accordance with an instruction from thecontroller 30.

The platform 11 is a plate member disposed approximately horizontallyand perpendicular to a vertical line VL. The platform 11, which has anapproximately rectangular shape in a plan view, has such a predeterminedarea that the three-dimensional object T to be formed is mountable. Anupper surface 11 a of the platform 11 is a surface on which thethree-dimensional object T to be formed is mounted, and is a flatsurface perpendicular to the vertical line VL.

To one side of the platform 11, a coupling arm 12 is coupled and extendsin the vertical line VL direction. A coupler 13, which is disposed on anupper portion of the coupling arm 12, is coupled to a guide rail 14disposed along the vertical line VL. In this state, the coupler 13 isdisposed to be movable in a longitudinal direction of the guide rail 14.When a drive mechanism (not illustrated) inside of the coupler 13operates based on a command from the controller 30, the platform 11,which is coupled to the coupler 13 through the coupling arm 12, moves upand down along the vertical line VL.

On the upper side of the platform 11, a guide rail 15 is disposed in themain scanning direction Y. On the guide rail 15, the head 20 is disposedto be movable in the main scanning direction Y. The head 20 includes aplurality of ink heads 21 (21S, 21W, 21Y, 21M, 21C, 21K, and 21CL), aroller unit 24, and ultraviolet (UV) light sources 25 (curer). The inkheads 21 extrude the respective ink composites. The roller unit 24 makesuniform the heights of layers of the extruded ink composites andflattens the layers. The ultraviolet light sources 25 irradiate each ofthe flattened layers of the ink composites with ultraviolet light tocure ultraviolet curable resins contained in the ink composites.

The head 20 includes a drive mechanism, not illustrated, in a coupler 16to couple the head 20 to the guide rail 15. The main scanning driver 40drives the drive mechanism based on a command from the controller 30 soas to move the head 20 in the main scanning direction Y along the guiderail 15.

One end and the other end of the guide rail 15 in the longitudinaldirection are supported by guide rails 17, 17 parallel to each other inthe sub-scanning direction X. On these guide rails 17, 17, the guiderail 15 is arranged to be movable in the sub-scanning direction Xperpendicular to the main scanning direction Y. In the embodiment, thesub-scanning driver 45 drives a drive mechanism, not illustrated, basedon a command from the controller 30 so as to move the guide rail 15 andthe head 20 in the sub-scanning direction X.

As illustrated in FIG. 3A, the ultraviolet light sources 25, 25 aredisposed on a lower surface 20 a of the head 20 opposed to the platform11 on both sides in the main scanning direction Y. Between theultraviolet light sources 25, 25, the plurality of ink heads 21 (21S,21W, 21Y, 21M, 21C, 21K, and 21CL), which extrude the ink composites,and the roller unit 24 are disposed side by side at a predeterminedinterval in the main scanning direction Y.

The ink heads 21 include a support material head 21S, a white ink head21W, a plurality of color ink heads (21Y, 21M, 21C, and 21K), and aclear ink head 21CL. The color ink heads 21 include a yellow ink head21Y, a magenta ink head 21M, a cyan ink head 21C, and a black ink head21K. The yellow ink head 21Y extrudes yellow ink (Y: Yellow). Themagenta ink head 21M extrudes magenta ink (M: Magenta). The cyan inkhead 21C extrudes cyan ink (C: Cyan). The black ink head 21K extrudesblack ink (K: Black). The yellow ink head 21Y, the magenta ink head 21M,the cyan ink head 21C, and the black ink head 21K are disposed in thisorder from one side to the other side in the longitudinal direction ofthe head 20 (lateral direction in FIG. 3B).

The support material head 21S, the white ink head 21W, the color inkheads 21 (21Y, 21M, 21C, and 21K), and the clear ink head 21CL areink-jet heads to extrude ink droplets of ultraviolet curable inks by anink-jet technology. These ink heads are located at a position in thesub-scanning direction (X direction) suitable for extruding purposes,and are disposed side by side at a predetermined interval in the mainscanning direction (Y direction).

It should be noted that publicly known ink-jet heads may be suitablyused as the support material head 21S, the white ink head 21W, the colorink heads 21 (21Y, 21M, 21C, and 21K), and the clear ink head 21CL.These ink-jet heads each include an array of nozzles on a surfaceopposed to the platform 11. The array of nozzles includes a plurality ofnozzles disposed side by side in the sub-scanning direction. Each of theink-jet heads is arranged to extrude ink droplets toward the platform 11from the array of nozzles of the ink-jet head.

A nozzle direction in which the plurality of nozzles are disposed isperpendicular to the main scanning direction. In a modification of theconfiguration of the ink-jet head, the main scanning direction and thenozzle array direction may intersect each other at an angle other than aright angle.

The arrangement in which the support material head 21S, the white inkhead 21W, the color ink heads 21 (21Y, 21M, 21C, and 21K), and the clearink head 21CL are arrayed should not be limited to the illustratedconfiguration but may be modified in various manners. For example, someof the ink-jet heads may be arranged at a position deviated from aposition of the other ink-jet heads in the sub-scanning direction. Thehead 20 may further include ink-jet heads of lighter variations of theabove-described colors and colors such as R (red), G (green), B (blue),and orange.

The color ink heads 21 (21Y, 21M, 21C, and 21K) are ink-jet heads toextrude ink droplets of the color inks having the colors different fromeach other. All of the inks (ink composites) extruded from the color inkheads 21 (21Y, 21M, 21C, and 21K) are coloring inks (ink compositescontaining coloring components) used for forming the colored region 52illustrated in FIG. 2. Each of these coloring inks is an ink compositecontaining a coloring component such as a coloring pigment, a bindercomponent such as an ultraviolet curable resin, a solvent component tomaintain the binder component and the coloring component in a dispersedstate, and various kinds of additives.

The white ink head 21W is an ink-jet head to extrude ink droplets ofwhite (W) ink. The white (W) ink composite is an ink mainly used forforming the inner build region 50 and the intermediate region 51 of thewhite ink (W) and the transparent ink (CL), as illustrated in FIG. 2.This ink is the white (W) ink composite containing a coloring componentsuch as a white pigment, a binder component such as an ultravioletcurable resin, a solvent component to maintain the binder component andthe coloring component in a dispersed state, and various kinds ofadditives.

The clear ink head 21CL is an ink-jet head to extrude ink droplets ofclear ink. In this case, the clear ink is a transparent (CL) ink. Thistransparent (CL) ink composite is an ink used for forming theintermediate region 51 containing the white (W) ink composite and thetransparent (CL) ink composite, and the colored region 52. This ink isthe transparent (CL) ink composite containing a binder component such asan ultraviolet curable resin, a solvent component to maintain the bindercomponent in a dispersed state, and various kinds of additives.

It suffices that the transparent ink composite is an ink capable offorming a transparent layer that has a light transmission ratio per unitthickness of 50% or more. When the light transmission ratio per unitthickness of the transparent layer is less than 50%, it is not desirablebecause light transmission is so inconveniently interrupted that thethree-dimensional object cannot assume a color as desired by subtractivemixture of colors. Preferably, an ink having a light transmission ratioper unit thickness of the transparent layer of 80% or more should beused. More preferably, an ink having a light transmission ratio per unitthickness of the transparent layer of 90% or more should be used.

The support material head 21S is an ink-jet head to extrude ink dropletsincluding a material of a support layer. This support ink (S) is an inkused for forming the support region 53 to surround and support an outercircumference of the three-dimensional object T. The ink is an inkcomposite containing a binder component, which is an ultraviolet curableresin and is a resin soluble in water after cured, a solvent componentto maintain the binder component in a dispersed state, and various kindsof additives.

A plurality of ultraviolet light sources 25, which is an exemplaryultraviolet light irradiator, generate ultraviolet light to cure theultraviolet curable inks. As the ultraviolet light sources 25, forexample, UVLEDs (ultraviolet LEDs) may be suitably used. Alternatively,as the ultraviolet light sources 25, metal halide lamps and mercurylamps may be also used.

The roller unit 24 is a configuration to flatten each layer of theultraviolet curable inks formed in producing the three-dimensionalobject T. In this embodiment, the roller unit 24 is disposed between arow of the color ink heads 21Y, 21M, 21C, and 21K, the white ink head21W, the clear ink head 21CL, and the support material head 21S, and theultraviolet light source 25 (UV2) on the other side. Thus, the rollerunit 24 is disposed at a position in the sub-scanning direction suitablefor flattening purposes relative to the row of the color ink heads 21Y,21M, 21C, and 21K, the white ink head 21W, the clear ink head 21CL, andthe support material head 21S. The roller unit 24 and the row of theseheads are disposed side by side in the main scanning direction.

In this embodiment, the roller unit 24 includes a roller 241, a blade242, and an ink recoverer 246.

The roller 241 is an exemplary flattener to flatten a surface of eachlayer of the inks formed by the ink-jet heads. In a main scanningoperation, for example, the roller 241 comes into contact with thesurface of the layer of the ink so as to flatten the layer of the ink.

The blade 242 is a blade member to remove the ink, which has beenscraped by the roller 241, from the roller 241. The ink recoverer 246 isa recoverer to recover the ink removed from the roller 241 by the blade242.

Formation of the three-dimensional object T by the forming apparatus 10will now be described. FIG. 4 illustrates three-dimensional data used information of the three-dimensional object T by the forming apparatus 10.The three-dimensional data corresponds to a cross-section of thethree-dimensional object T in FIG. 2. FIG. 5 is a diagram illustratingan ink layer La formed based on slice data of the a-th ink layer La whenthe three-dimensional object T is divided into N (positive integer) inklayers L in the height direction.

The forming apparatus 10 slices (divides) the three-dimensional object Tat a predetermined interval in the height direction to set the N inklayers L (L1 to Ln: n is an arbitrary positive integer), and forms anink layer L1, which is on the platform 11 side (lower side), to an inklayer Ln in sequence to form the three-dimensional object T.

Each of the ink layers L is formed by extruding the ink compositecontaining ultraviolet curable resin by the head 20 to form an ink layerof the ink composite before cured (uncured ink layer), and subsequentlyirradiating the uncured ink layer thus formed with ultraviolet light tocure the ink layer. In this case, the uncured ink layer is formed bygenerating slice data, which specifies each ink layer L (L1 to Ln), fromthree-dimensional data (3D data) of the three-dimensional object T, andcontrolling extrusion of the ink composite from each of the ink heads21S, 21W, 21Y, 21M, 21C, 21K, and 21CL based on the generated slicedata.

When the three-dimensional data (three-dimensional data of thethree-dimensional object T) indicating a distribution of the regions(the inner build region 50, the intermediate region 51, the coloredregion 52, and the support region 53) of the three-dimensional object Thas the content illustrated in FIG. 4, the three-dimensional data isdivided into N pieces in a build direction (height direction) of thethree-dimensional object T so as to generate slice data of each inklayer. Then, slice data of the a-th ink layer La, for example, will havethe content for forming the ink layer La illustrated in FIG. 5.

The slice data for forming the ink layer La illustrated in FIG. 5 istwo-dimensional data indicating a distribution of the regions (an innerbuild region portion 500, an intermediate region portion 510, and acolored region portion 520) in a cross-section (ink layer La) of thethree-dimensional object T, and a distribution of a support regionportion 530 surrounding an outer circumference of the colored regionportion 520. The two-dimensional data makes it possible to specify aposition on a plane onto which each of the ink composites is extruded,and an amount of extrusion of the ink composite.

In the forming apparatus 10, when each ink layer L is formed, thecontroller 30 controls extrusion of the ink composite from each of theink heads 21S, 21W, 21Y, 21M, 21C, 21K, and 21CL of the head 20 based onthe slice data while moving the head 20 in the main scanning directionY. Thus, the ink layer La is formed in such a manner that part (theinner build region portion 500, the intermediate region portion 510, thecolored region portion 520, and the support region portion 530) of therespective regions (the inner build region 50, the intermediate region51, the colored region 52, and the support region 53) exists in thedistribution specified by the slice data (see FIG. 5).

Specifically, the ink layer L is formed by performing a main scanningoperation and a sub-scanning operation in turn. The main scanningoperation is alternate repetition of a pass operation of extruding theink composite while moving the head 20 from one side (left side in FIG.3A) of the guide rail 15 to the other side (right side in FIG. 3A) ofthe guide rail 15 and a pass operation of extruding the ink compositewhile moving the head 20 from the other side to the one side of theguide rail 15. The sub-scanning operation is performed while moving thehead 20 in the sub-scanning direction X.

In the last pass operation of the main scanning operation, the ink layerL before cured (uncured build material layer) is flattened by the roller241, and the uncured build material layer is cured by ultraviolet lightemitted from the ultraviolet light sources 25 so as to form the inklayer L.

Thus, the plurality of ink layers L are deposited in the Z direction(height direction) to form the three-dimensional object T. Of the innerbuild region portions 500 of the ink layers, the inner build region 50is formed to have a three-dimensional shape corresponding to an externalshape of the three-dimensional object T. Of the intermediate regionportions 510 of the ink layers, the intermediate region 51 is formed tosurround the surface of the inner build region 50. Of the colored regionportions 520 of the ink layers, the colored region 52 is formed tosurround the surface of the intermediate region 51. Of the supportregion portions 530 of the ink layers, the support region 53 is formedto support the lower side of the three-dimensional object T.

The inner build region 50, the intermediate region 51, and the coloredregion 52 are arranged in this order to form the three-dimensionalobject T. Consequently, even if the surface of the three-dimensionalobject T finally obtained is viewed in any of the X, Y, and Zdirections, the three-dimensional object T will have the arrangement ofthe inner build region 50, the intermediate region 51, and the coloredregion 52 in this order. This makes it possible to recognize a colortone expressed by subtractive mixing.

Referring to a flowchart in FIG. 6, a forming process of thethree-dimensional object T will be described below. FIG. 6 is theflowchart of the forming process of the three-dimensional object Tperformed by the forming apparatus 10.

In the controller 30, after three-dimensional (3D) data of thethree-dimensional object T is input (Yes at step S101), the slice numberN (a number of the ink layers L) of the three-dimensional object T andthe number of main scanning operations (pass number M) at the time offorming each ink layer L are set (Yes at step S102). Then, at step S103,the controller 30 resets a value of a build counter CT1 to start formingthe three-dimensional object T anew. The build counter CT1 is a counterto count the number of formed ink layers. When the build counter CT1 hasa value “3”, for example, it refers to completion of forming a third inklayer.

Subsequently, at step S104, the controller 30 divides the 3D data inaccordance with the slice number N to generate slice data. Thus, Npieces of slice data are generated from the one set of 3D data.

At step S105, while moving the head 20 in the main scanning direction Yand the sub-scanning direction X, the controller 30 causes the ink heads21S, 21W, 21Y, 21M, 21C, 21K, and 21CL to extrude the respective inkcomposites to form an ink layer.

Specifically, in order to form an ink layer, the controller 30 performsreading of slice data of the ink layer L to be formed.

In the embodiment, the value of the build counter CT1 is referred tospecify which ink layer among n ink layers L1 to Ln the ink layer L tobe formed is. Thus, the controller 30 obtains slice data correspondingto the specified ink layer from the plurality of slice data generated atstep S104 described above. For example, when the value of the buildcounter CT1 is “0 (=zero)”, it refers to incompletion of forming a firstink layer L1, and consequently, slice data of the first ink layer L1 atthe lowermost position is to be obtained.

Then, while moving the head 20 from one side (the other side) to theother side (one side) in the main scanning direction Y, the controller30 performs pass operations to extrude the respective inks from thesupport material head 21S, the white ink head 21W, the color ink heads21 (21Y, 21M, 21C, and 21K), and the clear ink head 21CL of the head 20.

For every position (pixel) having a predetermined area on a build space(X-Y plane space) on the platform 11, the slice data specifies whetherthe respective inks are extruded from the support material head 21S, thewhite ink head 21W, the color ink heads 21 (21Y, 21M, 21C, and 21K), andthe clear ink head 21CL of the head 20, and specifies extrusion amountsof the inks in extrusion of the inks.

Consequently, in the pass operations of the head 20, when the supportmaterial head 21S, the white ink head 21W, the color ink heads 21 (21Y,21M, 21C, and 21K), and the clear ink head 21CL of the head 20 pass by apredetermined position specified by the slice data, the controller 30causes the ink heads to extrude the inks to form a new ink layer on theupper surface 11 a of the platform 11 or on an ink layer already formed.

An example of forming the ink layer La in FIG. 4 will now be described.In this example, the head 20 performs pass operations by moving from apredetermined position on the left side in FIG. 4 to a predeterminedposition on the right side in FIG. 4. From the left side in FIG. 4, theink layer La includes the support region 53, the colored region 52, theintermediate region 51, the inner build region 50, the intermediateregion 51, the colored region 52, and the support region 53 in thisorder.

In light of the above circumstances, when the support material head 21Spasses by an upper side of the support region 53, the controller 30causes the support material head 21S to extrude the ink (supportmaterial composite). When the white ink head 21W passes by an upper sideof the inner build region 50, the controller 30 causes the white inkhead 21W to extrude the ink (white (W) ink composite).

When the clear ink head 21CL and the white ink head 21W pass by an upperside of the intermediate region 51, the controller 30 causes these inkheads to extrude the inks (transparent (CL) ink composite and white (W)ink composite). When the white ink head 21W, the color ink heads 21(21Y, 21M, 21C, and 21K), and the clear ink head (21CL) pass by an upperside of the colored region 52, the controller 30 causes thecorresponding heads to extrude the ink composites in accordance with acolor tone represented in the colored region 52.

The controller 30 performs such pass operations of extruding the inkcomposites while moving the head 20 times of the pass number set at stepS102 described above so as to form a new ink layer. In the last passoperation, uncured ink layers of the white (W) ink composite, which havebeen extruded and deposited until then, are flattened, and irradiatedwith and cured by ultraviolet light.

When the colored region portion 520 is formed, the transparent (CL) inkcomposite is extruded in addition to the ink composite containing thecoloring component (Color). This is because the transparent (CL) inkcomposite is used as replenishment ink to replenish a filling density(ink filling density) of the ink composite containing the coloringcomponent (Color). In a case where the colored region portion 520 isonly formed of the ink composite containing the coloring component(Color), part of the colored region portion 520 in which a color (colordepth) to show finally is deep has a large amount of the ink compositewhereas part of the colored region portion 520 in which the color depthis small has a small amount of the ink composite. As a result, in thecolored region portion 520, the ink composite containing the coloringcomponent (Color) has different filling densities at differentpositions. Since an area where the filling density is small is thinnerthan an area where the filling density is large, the surface of thecolored region portion 520 becomes uneven and has voidsdisadvantageously. Unevenness and voids of the colored region portion520 cause irregular reflection and refraction of light incident on thecolored region 52 of the surface of the three-dimensional object Tfinally obtained. This may degrade the color tone assumed by the surfaceof the three-dimensional object T and cause the three-dimensional objectT to lose the shape.

In light of the above circumstances, in the embodiment, the transparent(CL) ink composite is used as the replenishment ink to make uniform thefilling density of the ink composite. This prevents unevenness and voidsfrom occurring on the surface of the colored region portion 520 so as toprevent the color tone assumed by the surface of the three-dimensionalobject T finally obtained from degrading and to prevent thethree-dimensional object T from losing the shape.

It should be noted that in forming the new ink layer at step S104, whenthe width of the ink heads 21 in the sub-scanning direction is largerthan the width of the ink layer to be formed, it is necessary to formpart (inner build region portion 500, intermediate region portion 510,colored region portion 520, and support region portion 530) of the inklayer anew adjacent to part (inner build region portion 500,intermediate region portion 510, colored region portion 520, and supportregion portion 530) of the ink layer that has been already formed at thetime. Consequently, in this case, the controller 30 causes the head 20to move for a predetermined distance in the sub-scanning direction X,and performs the predetermined number of pass operations so as to formthe whole ink layer La specified by the slice data.

When the forming processing of the ink layer at step S105 is ended, thecontroller 30 increments a value of the build counter CT1 by “1” at stepS106. This refers to completion of the one ink layer L.

Then, at step S107, the controller 30 confirms whether the value of thebuild counter CT1 reaches the slice number N set at step S102. When thevalue of the build counter CT1 is not equal to the slice number N (No atstep S107), the controller 30 shifts to processing at step S105.

Thus, after shifting to step S105, the controller 30 performs formingprocessing of a new ink layer. For example, when the value of the buildcounter CT1 at this point in time is “1”, this point in time refers to apoint in time at which formation of the first ink layer L1 is completed,and consequently, a second ink layer L2 from the bottom is to be formed.

Thus, until the value of the build counter CT1 becomes the slice numberN set at step S102, processing from step S105 to step S108 is repeatedto form and deposit ink layers L in sequence.

Then, when the value of the build counter CT1 reaches the slice number Nset at step S102, a confirmation at step S107 is affirmed (Yes at stepS107), and the controller 30 ends the forming processing of thethree-dimensional object T.

Thus, finally, the three-dimensional object T formed of the depositedink layers L is produced. For example, when the slice number N set atstep S102 is “50”, a three-dimensional object T formed of 50 depositedink layers L is produced.

Functions of a case in which the inner build region portion 500, theintermediate region portion 510, the colored region portion 520, and thesupport region portion 530 of the ink layer L are formed in theabove-described process will be described below. FIGS. 7A and 7Billustrate a distribution of the ink composites in an ink layer Lx atsome midpoint in forming the three-dimensional object T according to theembodiment and a surface state of the ink layer Lx. FIG. 7A is aschematic cross-sectional view of the ink layer Lx taken along the lineA-A in FIG. 5. FIG. 7B is a view of the ink layer Lx in FIG. 7A, asviewed in a direction indicated by the arrows A, and illustrates thedistribution of the ink composites in the ink layer Lx. FIGS. 8A and 8Billustrate a distribution of the ink composites of an ink layer La′ of athree-dimensional object Ta according to a comparative example and asurface state of the ink layer La′.

The inventor of the present disclosure has found that when surfaceroughness of the colored region 52 after removing the support region 53increases, the color quality of the formed three-dimensional object T isdegraded. The inventor conducted research and study on what increasesthe surface roughness of the colored region 52. The inventor hasrealized that in forming the ink layer L, as a degree of mixing of theink composite of the colored region 52 and the ink composite of thesupport region 53 at an interface between these regions increases, thesurface roughness of the colored region 52 after removing the supportregion 53 increases.

The inventor has further realized that (a) the inks themselves affect adegree of mixing of the inks at an interface between the colored regionportion 520 and the support region portion 530 of the ink layer L beforecured. The inventor has also realized that (b) interposition of theintermediate region portion 510 between the colored region portion 520and the inner build region portion 500 makes affinity between thecolored region portion 520 and the inner build region portion 500 higherthan affinity between the colored region portion 520 and the supportregion portion 530 so as to suppress mixing of the inks at the interfacebetween the colored region portion 520 and the support region portion530. In light of the above circumstances, the inventor has determined apositional relationship of the region portions (the inner build regionportion 500, the intermediate region portion 510, the colored regionportion 520, and the support region portion 530) of the ink layer L, anda composition of the ink composites in the intermediate region portion510.

Specifically, the intermediate region portion 510 between the innerbuild region 500 and the colored region portion 520 is arranged to be amixed region of the transparent (CL) ink composite and the white (W) inkcomposite.

An arrangement of the region portions (the inner build region portion500, the intermediate region portion 510, the colored region portion520, and the support region portion 530) of the ink layer L in this casehas a positional relationship illustrated in FIG. 7A. As illustrated inFIG. 7B, the transparent (CL) ink composite in the intermediate regionportion 510 is also contained in the colored region portion 520 outsideof and adjacent to the intermediate region portion 510. The white (W)ink composite is contained in the inner build region portion 500 insideof and adjacent to the intermediate region portion 510.

Thus, the intermediate region portion 510 and the colored region portion520 contain the transparent (CL) ink composite in common. Thistransparent (CL) ink composite makes affinity between the intermediateregion portion 510 and the colored region portion 520 higher thanaffinity of the intermediate region portion 510 and the colored regionportion 520 with the other regions.

The intermediate region portion 510 and the inner build region portion500 contain the white (W) ink composite in common. This white (W) inkcomposite makes affinity between the intermediate region portion 510 andthe inner build region portion 500 higher than affinity between theintermediate region portion 510 and the other region.

As a result, affinity between the inner build region portion 500 and thecolored region portion 520 through the intermediate region portion 510becomes higher than affinity between the colored region portion 520 andthe support region portion 530. This prevents the inks from mixing atthe interface between the colored region portion 520 and the supportregion portion 530.

This arrangement reduces the surface roughness of the colored regionportion 520 (colored region 52) after removing the support regionportion 530 (support region 53) so as to improve the color quality ofthe formed three-dimensional object T.

On the contrary, in the case of the ink layer La′ (see FIG. 8A) withoutthe intermediate region portion 510 according to the present disclosure,the inner build region portion 500 is on one side of the colored regionportion 520 whereas the support region portion 530 is on the other sideof the colored region portion 520. As illustrated in FIG. 8B, since thecolored region portion 520 does not contain the transparent (CL) inkcomposite, affinity between the colored region portion 520 and the innerbuild region portion 500 and affinity between the colored region portion520 and the support region portion 530 have no relative difference.

Consequently, at an interface between the colored region portion 520 andthe inner build region portion 500 and at an interface between thecolored region portion 520 and the support region portion 530, mixing ofthe ink composites equally occurs.

In this case, since the surface roughness of the colored region portion520 (colored region 52) after removing the support region portion 530(support region 53) cannot be controlled, the color quality of theformed three-dimensional object Ta cannot be stabilized.

In light of the above circumstances, in this embodiment, the arrangementof the region portions (the inner build region portion 500, theintermediate region portion 510, the colored region portion 520, and thesupport region portion 530) in each ink layer is set. This decreases thedegree of mixing of the ink composite in the colored region portion 520and the ink composite in the support region portion 530 at the interfacebetween these region portions. This reduces the surface roughness of thecolored region portion 520 (colored region 52) after removing thesupport region portion 530 (support region 53) so as to improve thecolor quality of the formed three-dimensional object T.

As described above, in this embodiment, (1) a method for forming athree-dimensional object (three-dimensional object T) by extruding inkdroplets from the ink-jet heads includes: an inner-build-region formingstep to form the inner build region 50 of the three-dimensional objectT; a colored-region forming step to form the colored region 52 outsideof the inner build region 50 so as to color the three-dimensional objectT; a support-region forming step to form the support region 53 (supportregion) outside of the colored region 52 so as to support thethree-dimensional object T while forming the object T; and anintermediate-region forming step to form the intermediate region 51between the inner build region 50 and the colored region 52. Theintermediate region 51 is formed in such a manner that affinity betweenthe intermediate region 51 and the inner build region 50 and affinitybetween the intermediate region 51 and the colored region 52 are higherthan affinity between the colored region 52 and the support region 53.

With this configuration, affinity between the colored region 52 and theinner build region 50 through the intermediate region 51 becomes higherthan affinity between the colored region 52 and the support region 53.This prevents inks from mixing at the interface between the coloredregion 52 and the support region 53. This configuration reduces surfaceroughness of the colored region 52 after removing the support region 53so as to improve the color quality of the formed three-dimensionalobject T.

(2) The method for forming the three-dimensional object T by depositingthe plurality of ink layers L1 to Ln in the height direction includes: afirst step to divide the three-dimensional object T into a plurality ofsections in the height direction to set the plurality of ink layers L1to Ln; a second step to generate slice data to specify each of theplurality of ink layers L1 to Ln based on three-dimensional data of thethree-dimensional object T; and a third step to control extrusion of theink composites from the respective ink heads 21 (21S, 21W, 21Y, 21M,21C, 21K, and 21CL) based on the slice data to form the ink layers L andto deposit the ink layers L in sequence to form the three-dimensionalobject T. The three-dimensional object T includes: the inner buildregion 50 having a shape corresponding to an external shape of thethree-dimensional object T and formed of the white (W) ink composite atleast on the surface side of the inner build region 50; the intermediateregion 51 formed of the white (W) ink composite and the transparent (CL)ink composite, and covering the surface of the inner build region 50;and the colored region 52 formed of an ink composite containing acoloring component (Color), and the transparent (CL) ink composite. Thecolored region 52 covers the surface of the intermediate region 51. Theink layers L include: ink layers each including the inner build regionportion 500 to be part of the inner build region 50, the intermediateregion portion 510 to be part of the intermediate region 51, and thecolored region portion 520 to be part of the colored region 52; and inklayers with the support region portions 530 surrounding the coloredregion portions 520. The support region portions 530 support the lowersurfaces of other ink layers deposited on the upper side of thethree-dimensional object T in the height direction. The method furtherincludes a fourth step to remove the support region 53 after forming thethree-dimensional object T by depositing the plurality of ink layers L.

With this configuration, the intermediate region 51 includes the white(W) ink composite, which has high affinity to the white (W) inkcomposite in the inner build region portions 500. The intermediateregion 51 also includes the transparent (CL) ink composite, which hashigh affinity to the transparent (CL) ink composite among the inkcomposites constituting the colored region portions 520 other than theink composite containing the coloring component. As a result, affinitybetween the inner build region 50 and the colored region 52 through theintermediate region 51 becomes higher than affinity between the coloredregion 52 and the support region 53. This suppresses mixing of the inksat the interface between the colored region 52 and the support region 53(see FIG. 7B). This configuration makes it possible to reduce surfaceroughness of the colored region portions 520 (colored region 52) afterremoving the support region portions 530 (support region 53) so as toimprove the color quality of the formed three-dimensional object T.

The present disclosure is specifiable as the forming apparatus 10 of thethree-dimensional object T.

(3) The forming apparatus 10 of the three-dimensional object T includes:the platform 11 for the three-dimensional object T; the head 20 disposedmovably in the main scanning direction Y on the upper side of theplatform 11; the controller 30 (controller) to control movements of thehead 20 in the main scanning direction Y and extrusion of the inkcomposites from the respective ink heads 21S, 21W, 21Y, 21M, 21C, 21K,and 21CL of the head 20; and the ultraviolet light sources 25 (curer) tocure the ink composites extruded from the head 20. The forming apparatus10 forms ink layers L by curing the ink composites extruded from thehead 20 and deposits the ink layers L in the height direction so as toform the three-dimensional object T. The three-dimensional object Tincludes: the inner build region 50 having a shape corresponding to anexternal shape of the three-dimensional object T; the intermediateregion 51 covering the surface of the inner build region 50; and thecolored region 52 covering the surface of the intermediate region 51.The intermediate region 51 contains the ink composites to increaseaffinity between the intermediate region 51 and the inner build region50 and affinity between the intermediate region 51 and the coloredregion 52.

With this configuration, affinity between the inner build region 50 andthe colored region 52 through the intermediate region 51 becomes higherthan affinity between the colored region 52 and the other region. Thissuppresses mixing of the inks at the interface between the coloredregion 52 and the region other than the three-dimensional object T so asto reduce surface roughness of the three-dimensional object T. Thus, thethree-dimensional object T finally obtained has a surface with animproved color quality.

(4) The inner build region 50 is formed of the white (W) ink compositeat least on a surface side of the inner build region 50. The coloredregion 52 is formed of an ink composite containing a coloring component,and the transparent (CL) ink composite. The intermediate region 51 isformed of the white (W) ink composite and the transparent (CL) inkcomposite.

This configuration increases affinity between the intermediate region 51and the inner build region 50 and affinity between the intermediateregion 51 and the colored region 52. As a result, through theintermediate region 51, affinity between the colored region 52 and theinner build region 50 is increased to suppress mixing of the inks at theinterface between the colored region 52 and the support region 53.

Moreover, the present disclosure is specifiable as a non-transitorycomputer-readable storage medium storing a program for causing theforming apparatus 10 to execute processing for forming thethree-dimensional object T.

(5) In the non-transitory computer-readable storage medium storing theprogram for causing the forming apparatus 10 to execute processing forforming the three-dimensional object T by depositing a plurality of inklayers L in the height direction, the processing includes: causing thecontroller 30 (controller) for the forming apparatus 10 to divide thethree-dimensional object T into a plurality of sections in the heightdirection to set the plurality of ink layers L (FIG. 6: step S102);causing the controller 30 to generate slice data to specify each of theplurality of ink layers L based on three-dimensional data of thethree-dimensional object T (FIG. 6: step S104); and causing thecontroller 30 to control extrusion of the ink composites from therespective ink heads 21S, 21W, 21Y, 21M, 21C, 21K, and 21CL based on theslice data so as to form the ink layers, and deposit the ink layers insequence so as to form the three-dimensional object T (FIG. 6: stepsS105 to S108). The three-dimensional object T includes: the inner buildregion 50 having a shape corresponding to an external shape of thethree-dimensional object T; the intermediate region 51 covering thesurface of the inner build region 50; and the colored region 52 coveringthe surface of the intermediate region 51. The intermediate region 51includes ink composites for increasing affinity between the intermediateregion 51 and the inner build region 50 and affinity between theintermediate region 51 and the colored region 52.

This configuration makes it possible to improve the color quality of thesurface of the three-dimensional object T finally obtained.

Obviously, numerous modifications and variations of the presentdisclosure are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, thepresent disclosure may be practiced otherwise than as specificallydescribed herein.

Features of the present invention will now be extracted and described.

(1) The method for forming the three-dimensional object by extruding inkdroplets from the ink-jet heads includes: the inner-build-region formingstep to form the inner build region of the three-dimensional object; thecolored-region forming step to form the colored region outside of theinner build region so as to color the three-dimensional object; thesupport-region forming step to form the support region outside of thecolored region so as to support the three-dimensional object whileforming the object; and the intermediate-region forming step to form theintermediate region between the inner build region and the coloredregion. The intermediate region is formed in such a manner that affinitybetween the intermediate region and the inner build region and affinitybetween the intermediate region and the colored region are higher thanaffinity between the colored region and the support region.

With this configuration, affinity between the colored region and theinner build region is increased to prevent the inks from mixing at theinterface between the colored region and the support region.

(2) In the method for forming the three-dimensional object described in(1), the inner build region is formed of the white ink composite atleast on the surface side of the inner build region. The colored regionis formed of the ink composite containing the coloring component, andthe transparent ink composite. The intermediate region is formed of theink composite containing the coloring component, and the transparent inkcomposite.

This configuration makes affinity between the inner build region and thecolored region through the intermediate region higher than affinitybetween the colored region and the support region. This prevents theinks from mixing at the interface between the colored region and thesupport region (see FIG. 7B). This configuration reduces the surfaceroughness of the colored region after removing the support region so asto improve the color quality of the formed three-dimensional object.

(3) The three-dimensional-object forming apparatus includes: theplatform for the three-dimensional object; the head disposed movably inthe main scanning direction on the upper side of the platform; thecontroller to control movements of the head in the main scanningdirection and extrusion of the ink composites from the head; and thecurer to cure the ink composites extruded from the head. The apparatusforms ink layers by curing the ink composites extruded from the head anddeposits the ink layers in the height direction so as to form thethree-dimensional object. The three-dimensional object includes: theinner build region having a shape corresponding to an external shape ofthe three-dimensional object; the intermediate region covering thesurface of the inner build region; and the colored region covering thesurface of the intermediate region. The intermediate region is formed ofthe ink composites to increase affinity between the intermediate regionand the inner build region and affinity between the intermediate regionand the colored region.

This configuration makes affinity between the inner build region and thecolored region through the intermediate region higher than affinitybetween the colored region and the other region. This prevents the inksfrom mixing at the interface between the three-dimensional object andthe object other than the three-dimensional object so as to reduce thesurface roughness of the three-dimensional object. Thus, thethree-dimensional object finally obtained has an improved surface colorquality.

(4) In the three-dimensional-object forming apparatus described in (3),the inner build region is formed of the white ink composite at least onthe surface side of the inner build region. The colored region is formedof the ink composite containing the coloring component, and thetransparent ink composite. The intermediate region is formed of the inkcomposite containing the coloring component, and the transparent inkcomposite.

This configuration increases affinity between the intermediate regionand the inner build region and affinity between the intermediate regionand the colored region. As a result, through the intermediate region,affinity between the colored region and the inner build region isincreased to suppress mixing of the inks at the interface between thecolored region and the support region.

(5) The non-transitory computer-readable storage medium storing theprogram for causing the three-dimensional-object forming apparatus toexecute processing for forming the three-dimensional object bydepositing the plurality of ink layers in the height direction. Theprocessing includes: causing the controller for thethree-dimensional-object forming apparatus to divide thethree-dimensional object into the plurality of sections in the heightdirection to set the plurality of ink layers; causing the controller togenerate slice data to specify each of the plurality of ink layers basedon three-dimensional data of the three-dimensional object; causing thecontroller to control extrusion of the ink composite from each ink headbased on the slice data so as to form the ink layers; causing thecontroller to cure the ink layers formed at the extrusion controllingstep; and causing the controller to repeat the slice-data generatingstep and the extrusion controlling step to deposit the ink layers insequence so as to form the three-dimensional object. Thethree-dimensional object includes: the inner build region having a shapecorresponding to an external shape of the three-dimensional object; theintermediate region covering the surface of the inner build region; andthe colored region covering the surface of the intermediate region. Theintermediate region includes ink composites for increasing affinitybetween the intermediate region and the inner build region and affinitybetween the intermediate region and the colored region.

This configuration improves the color quality of the surface of thethree-dimensional object finally obtained.

-   10 forming apparatus-   11 platform-   12 coupling arm-   13, 16 coupler-   14, 15, 17 guide rail-   20 head-   21C, 21M, 21Y, 21K, 21S, 21W, 21CL ink head-   25 ultraviolet light source-   24 roller unit-   241 roller-   242 blade-   30 controller-   40 main scanning driver-   45 sub-scanning driver-   50 inner build region-   500 inner build region portion-   51 intermediate region-   510 intermediate region portion-   52 colored region-   520 colored region portion-   53 support region-   530 support region portion-   A plane-   CT1 build counter-   CAD three-dimensional-   L (L1, . . . , La, . . . Ln) ink layer-   T three-dimensional object-   X sub-scanning direction-   Y main scanning direction

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A method for forming a three-dimensional objectby extruding ink droplets from ink-jet heads, the method comprising:forming an inner build region of the object; forming a colored regionoutside of the inner build region so as to color the object; forming asupport region outside of the colored region so as to support the objectwhile forming the object; and forming an intermediate region between theinner build region and the colored region, the intermediate region beingformed in such a manner that affinity between the intermediate regionand the inner build region and affinity between the intermediate regionand the colored region are higher than affinity between the coloredregion and the support region, wherein the inner build region comprisesa white ink composite at least on a surface side of the inner buildregion, wherein the colored region comprises an ink composite comprisinga coloring component, and a transparent ink composite, and wherein theintermediate region comprises the ink composite comprising the coloringcomponent, and the transparent ink composite.